Externally threaded fastener pins are widely used in aircraft and aerospace structures. The pins have a head, a shank, and an external thread on the shank. The pins are pulled into holes in the structure so the head bears against the structure, and the thread projects beyond it. Then a threaded fastener is turned on to the threads and tightened down to a correct torque level.
Substantial force must be expected to be required to seat a properly dimensioned fastener with an interference in a properly dimensioned hole in the workpiece. In modern practice, percussive blows on the head of the fastener to seat the fastener are not acceptable. Instead a strong pull on the shank is required.
There are various means known to accommodate a pulling device. Obviously the thread on the fastener itself is not available for the purpose because it will fit too closely in the hole as it passes through it. Various extensions of the shank have been suggested. One kind is integral with the shank and must be broken or cut off. While this is useful for some sizes of fasteners and kinds of installations, it has the disadvantage of being formed from the same blank as the remainder of the fastener, and of the same material. This complicates the manufacture, and when the material is costly, is inherently wasteful. It has the additional disadvantage that in order to accommodate a very thick workpiece and a substantial tool, the extension would have to be much too long.
These disadvantages have been recognized, and in U.S. Pat. No. 5,098,238 issued Mar. 24, 1992 to Batchelor et al, a puller is shown threaded into an internally threaded recess in the threaded end. This enables the puller to be removed without cutting and wasting material. It can be re-used as part of a pulling tool instead of as a wasted part of the fastener, and can be made with very strong threads.
While the Batchelor device generally performs well, there are certain circumstances for which improvement is indicated. When a fastener is pulled into a hole and makes an optimum interference fit, the torque exerted on the nut or collar when tightened will be fully resisted by the fastener. However, occasionally even within proper tolerances, the interference fit is not that tight, and some kind of restraint is needed. This is a particular problem if the head is not accessible, or is not provided with wrench-engaging means.
It is an object of this invention to provide a removable puller which can also resist rotation of the pin while the collar or nut is tightened, without complicating the structure of the fastener or of the tool used to set the fastener.